a) Field of the Invention
The invention is directed to a device for generating operating states characterized by differences in height in mechanical actuators such as those preferably used for tactile representation of braille text and for adapters in circuit board testers.
b) Description of the Related Art
Actuators which can be vertically adjusted mechanically are often arranged in matrix form in technical applications to realize different operating states. For example, in known adapters for circuit board testers, contact needles are plugged in manually or by means of specific handling techniques in a grid or raster in matrix form corresponding to the measurement task at hand. In some instances, this is very time-consuming and its use is limited to existing adapters.
Other devices for producing vertically adjusted actuators which are required to be selectively controllable are known for representing braille text, in particular in computer display modules or typewriter display modules. In principle, there are two different methods of realization. On the one hand, piezoelectric deflection elements or bending elements are used for vertical adjustment. These bending elements being limited to row or line arrangements due to their required constructional size. On the other hand, hydraulic systems are known which achieve matrix arrangements and are operated via electroviscous liquids. An example of such a device is disclosed in DE-OS 40 07 945. In this case, the display elements are realized by hydraulically adjustable lifting elements and are operated in that periodic changes in pressure at appropriate frequencies are impressed on the liquid in a reservoir so that the pressure curve at all control channels or control ducts has only small phase differences. A control electrode in every control duct is connected to d.c. voltage at the same frequency at which the changes in pressure are effected. The value of the phase angle between the changes in pressure and the voltage pulses regulates the volume in the work space of the display element and accordingly the tactile opposing pressure of the display element.
A disadvantage consists in that only small actuating or adjusting paths and small pressure differences can be produced. Further, circulation of the electroviscous liquid is impossible, which fosters separating processes.